First of all, you need to know that there's a lot of documentation about how to install popular applications in Arch Linux, accessible from the Arch User Repository (AUR) community-driven Wiki. Click the link to access it, and don't forget to bookmark it, as you will always need it.

Second of, we should inform you about the method used to install third-party applications in Arch Linux, as the distro uses source packages and a clever method to grab them, compile them (if necessary) and install them. See below for a detailed example.

Keep in mind, though, that some third-party apps need third-party dependencies, which have to be installed first, using the method below.

Therefore, access the AUR Package Database web page, and bookmark it. Now, every time you need to install a package, you should open the aforementioned page and search the respective package.

The Manual Way

Let's say we want to install the Dropbox client for Linux. Of course, the official Dropbox Linux download page doesn't offer a proper package for Arch Linux nor any other Linux operating system. So you need to access the Arch Linux Package Database page and search for Dropbox.

Access the AUR Package Database web page listed above and search the application you want to install. Some queries will output many results, so try to access the one that is more appropriate for your needs.

For example, searching for "dropbox" will output 51 packages, but the one we need is called "dropbox 2.0.21-1." You can also re-arrange the search results after votes, and you will see that dropbox is the first one.

Access the page, and you will see something like this...

Note: Actually, this is how all the package details pages look like on the Arch User Repository (AUR) website.

So, to install any third-party package in Arch Linux, you need to click the "Download tarball" entry from the Package Actions frame in the right side. See the photo above for details or access the page yourself and execute these instructions while reading.

Download and save the archive on your desktop, extract it, and open the folder. Open a terminal in the respective folder and type the following command:

makepkg -s

Hit the Enter key and wait for the process to finish. The above command will download official source or binary package, extract it, download and install the dependencies (if needed), compile the source package (if necessary) and generate an Arch Linux binary package.

When it's done, an Arch Linux package will be created in the current folder. All you have to do is install it, using the following command:

sudo pacman -U packagename

Note: Replace "packagename" in the above command with the complete name of the package, including the file type. E.g. sudo pacman -U dropbox-2.0.21-1-x86_64.pkg.tar.xz

Hit the Enter key, and again when asked, and wait for the package to be installed. That's it! Dropbox is now installed in your Arch Linux operating system.

The Easy Way

This is the recommended way to install third-party packages in Arch Linux, using two applications: cower and meat. Of course, both packages can be installed using the "The Manual Way" above.

After installation, you will be able to install third-party applications in Arch Linux using the following command:

meat -d packagename

Don't forget, you can also use the meat utility to update packages installed with it, using the following command:

meat -u

Do not hesitate to comment below in case you run into trouble. Have fun using Arch Linux!